The missing Malaysian plane could be at the bottom of the Indian Ocean, according to a new report.

A US official has reportedly said there's a "likelihood'' the missing plane is at the bottom of that ocean, according to CNN.

The engines of a missing Malaysian airliner continued to operate for about four hours after it disappeared from radar over the Gulf of Thailand, US authorities say, providing a tantalising new lead in a case that has baffled Malaysian authorities and turned into one of the biggest aviation mysteries in history.

As a result of unspecified "new information", White House spokesman Jay Carney said earlier today that authorities searching for the plane may expand the hunt into the Indian Ocean, which extends hundreds of kilometres farther west.

Obama administration officials later said the new information was that the plane's engines remained running for approximately four hours after it vanished from radar early on Saturday en route from Kuala Lumpur, Malaysia, to Beijing.

There were 239 people on board the plane. Two of them were New Zealanders.

One senior administration official said the data showing the plane engines running hours after contact was lost came from the Aircraft Communications Addressing and Reporting System, or ACARS, a way that planes maintain contact with ground stations through radio or satellite signals. The official said Malaysian authorities shared the flight data with the administration.

The Boeing 777-200 was sending out a signal to establish contact wtih a satellite, an official told AP.

Boeing offers a satellite service that can receive a stream of data during flight on how the aircraft is functioning. Malaysia Airlines didn't subscribe to that service, but the plane still had the capability of connecting with the satellite and was automatically sending pings, the official said.

"It's like when your cellphone is off but it still sends out a little 'I'm here' message to the cellphone network," the official said. "That's how sometimes they can triangulate your position even though you're not calling because the phone every so often sends out a little bleep. That's sort of what this thing was doing."

The continuing pings led searchers to believe the plane could have flown more than 1600km beyond its last confirmed sighting on radar, the official said. The plane had enough fuel to fly about four more hours, he said.

Messages involving a different data service also were received from the airliner for a short time after the plane's transponder - a device used to identify the plane to radar - went silent, the official said.

The Wall Street Journal first reported that US investigators suspect that the engines kept running for up to four more hours after the plane reached its last known location. The paper later corrected its report to say that this belief was based on satellite data, not signals from monitoring systems embedded in the plane's Rolls-Royce engines. The Malaysian government denied the initial report.

The developments came as the government in Kuala Lumpur acknowledged that it has made little progress in solving the mystery of the vanished plane.

The US officials said they did not know what direction the plane flew — or whether it simply circled — during the approximately four hours or whether it was airborne at all. But that stretch of additional flight time could have put the plane somewhere over the Indian Ocean, prompting US officials to consider expanding the search into that area.

The officials spoke on condition of anonymity to discuss details of the investigation.

In a news conference, Malaysia's defence minister and a Malaysia Airlines chief executive played down or dismissed a series of leads that had led to frenzied speculation about the fate of Malaysia Airlines flight 370, which went missing nearly a week ago in a case that has become more difficult by the day.

In what Malaysian officials describe as an unprecedented aviation mystery, it remains unknown whether the plane, which carried 239 passengers and crew, is on land or in water, east of the country or to the west, or even somewhere far beyond.

In Washington, Carney told reporters that the United States is not in a position to draw any conclusions. However, he added, "it's my understanding that based on some new information that's not necessarily conclusive — but new information — an additional search area may be opened in the Indian Ocean".

Search operations in the Indian Ocean, the world's third-largest ocean with an average depth of nearly 12,800 feet (3.9km), would present significant challenges.

The United States is "consulting with international partners about the appropriate assets to deploy", Carney said at a White House news briefing on Thursday (local time).

Pressed for details, Carney said that "one possible piece of information or . . . pieces of information has led to the possibility that a new . . . search area may be opened in the Indian Ocean, but I don't have any more details on that".

Adding to the confusion, Lieutenant Colonel Jeffrey Pool, a Pentagon spokesman, said the Defense Department has no reason to believe that the plane crashed in the Indian Ocean. He said US Navy assets participating in the search are being guided by the Malaysian government's investigation. He said he did not know what new information Carney was referring to.

Hishammuddin Hussein, Malaysia's defence minister and acting transport minister, said in Kuala Lumpur: "We have looked at every lead. In many cases, in fact all the cases, we have not found anything positive." He added, "Without debris, we can't feel we are making any progress."

As the search area continued to widen, the US Navy said it was shifting one of its ships involved in the hunt, the destroyer USS Kidd, from the Gulf of Thailand northeast of Malaysia to the Strait of Malacca on the western side of the Malay Peninsula.

The US military also announced that it would add a P-8A Poseidon aircraft to the search on Friday. That plane is described by its manufacturer, Boeing, the world's most sophisticated "long-range anti-submarine warfare, anti-surface warfare, intelligence, surveillance and reconnaissance aircraft". It will join a Navy P-3C Orion surveillance aircraft already patrolling as part of the massive international operation.

India's Defense Ministry said Thursday that the Indian navy has launched its own search mission, sending two ships — the INS Kumbhir, an amphibious warfare ship, and the INS Saryu, a patrol vessel — into the Andaman Sea near the Malacca Strait. India also appointed Air Marshal AK Roy as co-ordinator for rescue operations with Malaysian authorities.

Indian coast guard and navy aircraft were also pressed into service from a base on the Andaman and Nicobar Islands. A senior Indian official said late on Thursday that a total of three ships, two planes and a helicopter have now been dispatched in the growing search effort.

Burma said it would open its airspace to planes looking for the missing airliner and was prepared to join the search if asked, the BBC reported.

Flight 370 was initially supposed to follow a northern path to Beijing. Search teams from as many as 12 nations have been scouring the waters to the east and west of Malaysia. Earlier on Thursday, attention focused on satellite images from a Chinese agency that showed three large objects in the water south of Vietnam. But by midday, Malaysian authorities were dismissing the likelihood that those objects belonged to the plane.

Both Malaysian and Vietnamese teams returned on Thursday to the co-ordinates of the large objects but found nothing.

Even as viewed by satellite, the objects didn't seem to match that of a plane wreck. The largest of the objects was roughly the size of a basketball court, with no smaller debris around. The Chinese Embassy in Malaysia notified the Malaysian government on Thursday, saying the images — released by a relatively unknown Chinese agency — were made public by mistake and did not relate to Flight 370.

Hishammuddin said it remained possible that the plane turned around, diverting to the west after disappearing from radar. But he added that the search was still focused around the location where the plane vanished. Of 46 ships involved in the search, 26 are in the Gulf of Thailand and the South China Sea, and 17 on the western side, in the Strait of Malacca and Andaman Sea.

"Our main effort has always been in the South China Sea," Hishammuddin said.

Malaysia has been criticised for at times releasing partial or contradictory information about the flight and search. The criticism has been most pointed from China, which had 153 citizens on the flight. Chinese Premier Li Keqiang said Thursday that Beijing had "asked the relevant party to enhance co-ordination" and find the plane as quickly as possible.

"First, this situation is unprecedented," Hishammuddin said, in deflecting the criticism. "MH370 went completely silent while over the open ocean. We are in the middle of a multi-national search involving many countries. This is a crisis situation. It is a very complex operation. And it has not always been easy."

But, he added, "We have not done anything that could jeopardise this search effort."

Malaysia Airlines announced separately on Thursday that "as a mark of respect to the passengers and crew of MH370" who disappeared on March 8, it will retire the MH370 and MH371 flight codes it has used on its routes to and from Beijing. MH is the designation for Malaysian Airline System, as the carrier is officially named.